1. Field of the Invention
The present application relates generally to an improved data processing system and method. More specifically, the present application is directed to an on-demand allocation of virtual asynchronous services interfaces.
2. Background of the Invention
Virtualization of computing resources is important in current computer environments. International Business Machine's POWER™ hypervisor, which is part of the firmware in Power™ systems, allows the virtualization of physical processors, memory, and I/O devices. Hypervisor is a virtual manager that partitions a system into multiple virtual machines and manages the system's resources across the virtual machines. These partitions can use whole physical processors or a fractional part of a whole physical processor. Each partition is assigned virtual processors that get mapped to a whole or a fractional part of physical processors by the hypervisor.
Within a virtualized server environment, certain virtual Input/Output (I/O) functions may be provided via a special service logical partition (LPAR) commonly referred to as a Virtual I/O Server (VIOS). In order to provide these functions, the VIOS may need to be able to communicate with the partition management firmware, e.g. a hypervisor. A Virtual Asynchronous Services Interface (VASI) is one example of an interface that provides a communication channel for the VIOS to communicate with the partition management firmware. For example, a VIOS can provide a Mover Service Partition (MSP) service to extract, migrate, and install the partition state of other LPARs on the same server to another (destination) server. The MSP may obtain these partition states from the partition management firmware using a VASI device.
VASI adapters, like all virtual device types, require memory overhead by the partition management firmware. Memory is a constrained resource and, hence, it is beneficial to limit this overhead. Therefore, always having VASI adapters allocated to a VIOS in a virtualized server environment may be wasteful, especially if that VIOS is never intended to provide services requiring a VASI adapter. Since LPARs cannot allocate hardware resources to themselves, the LPARs operate in isolation in that they are unaware of those server resources outside those that are assigned to them. Furthermore, the partition management firmware is not capable of allocating VASIs itself as the partition management firmware would then face a “chicken-or-egg” scenario where to notify the VIOS that the partition management firmware has allocated a VASI adapter, the partition management firmware would need a VASI adapter to do so.